During the processing of microelectronic workpieces into, for example, electronic devices such as integrated circuits, it is necessary to clean the surface of the workpiece by removing contaminants. Contaminants not removed during cleaning process tend to reduce the overall yield of the manufacturing process. This reduces the number of usable electronic components, such as integrated circuits, microprocessors, memory devices, etc. that can be obtained from a workpiece.
During the processing of microelectronic workpieces, chemical-mechanical polishing (“CMP”) is sometimes employed to planarize or polish the surface layers of the microelectronic workpiece. Typically, during the CMP process, the microelectronic workpiece is typically pressed against a slurry on a polishing pad under controlled conditions. The slurry used in the CMP process generally includes small, abrasive particles that mechanically remove the surface layer of the microelectronic workpiece. The slurry also contains chemicals that chemically remove the surface layer. After the microelectronic workpiece is polished, it is necessary to remove the residual particles on the surface of the microelectronic workpiece that were introduced during the CMP process. Contaminants may be introduced by the slurry, the polishing pad, or from features formed on the microelectronic workpiece. These contaminants are removed in a post-CMP cleaning process.
Current post-CMP cleaning processes have typically employed a brush scrub, spray cleaning, or immersion process to remove the contaminants introduced during the CMP process. Each of these post-CMP cleaning processes, however, have particular problems when the microelectronic workpiece includes copper (Cu) features. In recent years, microelectronic workpieces having copper-based features have been increasingly used because of copper's ability to efficiently and quickly transmit electrical current. The copper ion, however, is a highly mobile contaminant that poses particular problems for post-CMP cleaning processes.
Brush scrubbing is not favored for post-CMP cleaning of microelectronic workpieces containing copper because the scrubbing can damage the surface of the microelectronic workpiece. Since copper is relatively soft compared to other interconnect materials, aggressive brush scrubbing of the microelectronic workpiece can cause scratching or smearing of the copper features. Brush scrubbing may also further imbed particles into the surfaces of the copper features. Moreover, brush scrubbing is not able to adequately remove contaminants that are located on the edge region of the microelectronic workpiece.
Immersion techniques may avoid these drawbacks. However, as they generally use recirculated chemicals, they may cause unwanted copper redeposition.
Spray cleaning may avoid the disadvantages of both brush and immersion cleaning. However, spray cleaning may not be as effective in cleaning the microelectronic workpiece.
As copper ion's are highly mobile, they can also easily contaminate fabrication equipment. For example, copper contamination on the back side of the microelectronic workpiece can be transported to wafer handlers, indexers and chucks. Copper contamination can also be transported to cassettes, boxes, and indexer devices.
Accordingly, there remains a need for improved post-CMP cleaning methods and devices for cleaning copper from the front, back, and edge of a microelectronic workpiece, while maintaining the integrity of the copper features on the microelectronic workpiece. A method and apparatus is needed for reducing particle contamination from the sides and edge of the microelectronic workpiece without damage to the copper features that are typically located on the front side of the microelectronic workpiece. There is also a need at the same time to keep copper oxide at low levels.